The present invention relates generally to a sterilisation apparatus and a method of sterilisation and relates particularly, though not exclusively, to sterilisation involving ultrasonic nebulisation of a sterilising agent such as hydrogen peroxide.
It is recognised that the sterilisation of equipment can be achieved by exposing the equipment to an ultrasonically nebulised sterilising agent such as hydrogen peroxide. The sterilising agent is provided as an aerosol which effectively penetrates crevices, pores and other portions of the equipment which otherwise are not accessible by sterilizing agent in a liquid form.
Several US patents including U.S. Pat. No. 4,424,189 (Hick), U.S. Pat. No. 4,797,255 (Hatanaka et al), and U.S. Pat. No. 4,512,951 (Koubek) disclose the heating of a sterilising agent to effect evaporation of the sterilising agent which in its gaseous form is then contacted with the equipment to be sterilised. Although the gaseous sterilising agent is effective in penetrating the equipment the apparatus covered by these patents have the following drawbacks:
i) the apparatus is generally complicated in construction;
ii) the apparatus must be formed of materials resistant to the relatively high temperatures at which it is operated; and
iii) the choice of sterilising agents is restricted by the relatively high operating temperature.
Other US patents including U.S. Pat. No. 4,680,163 (Blidschun et al) and U.S. Pat. No. 4,366,125 (Kodera) describe ultrasonic nebulisation of a sterilising agent at ambient temperature. In these examples of the prior art an aerosol of the sterilising agent may condense on the equipment for effective sterilisation in the liquid form. However, the sterilising agent within the aerosol is of a low concentration as it is diluted with a carrier gas and/or the flow of the carrier gas and the aerosol is intermittent.
An intention of the present invention is to provide a sterilisation apparatus and a method of sterilisation that in operation are relatively effective.
According to one aspect of the present invention there is provided a sterilisation apparatus comprising:
an aerosol generator being adapted to generate an aerosol of a sterilising agent; and
a sterilisation chamber operatively coupled to the aerosol generator so as to receive a recirculatory flow of the aerosol, the sterilisation chamber being designed to receive an article requiring sterilisation whereby in operation the recirculatory flow of the aerosol through the sterilisation chamber is effective in sterilising the article.
According to another aspect of the present invention there is provided a sterilisation chamber being adapted to receive an article requiring sterilisation, the sterilisation chamber including an inlet and an outlet being configured to receive a recirculatory flow of an aerosol of a sterilising agent whereby in operation the recirculatory flow of the aerosol through the sterilisation chamber is effective in sterilising the article.
Generally the aerosol generator includes an ultrasonic transducer operatively coupled to or forming part of a reservoir which is adapted to contain the sterilising agent.
Preferably the sterilisation apparatus further comprises a tube positioned above the reservoir, the ultrasonic transducer being effective in producing a fountain of the sterilising agent into an inlet of the tube where the aerosol is produced. It is understood that the aerosol is produced from a lower part of the fountain and the kinetic energy of the fountain within the tube increases the static pressure of the aerosol within the tube thereby inducing a pressure drop across the tube which alone serves to propel the aerosol.
Typically an outlet of the tube is coupled to or defines the inlet of the sterilisation chamber. More typically the outlet of the sterilisation chamber is coupled to or defines an air inlet, the aerosol being propelled through the tube under the assistance of air being drawn through the air inlet.
Preferably the apparatus further comprises means for effecting condensation of the aerosol within or on the article. Typically said means includes one or more of the following contrivances:
i) a heating element operatively coupled to the inlet of the sterilisation chamber;
ii) an ultrasonic transducer operatively coupled to the sterilisation chamber; and/or
iii) a device for increasing the pressure of aerosol within the sterilisation chamber.
Typically the apparatus also comprises means for rinsing and/or drying the condensed aerosol within or on the sterilisation chamber together with the article. Generally said rinsing and/or drying means is of a conventional construction.
Typically the aerosol generator and/or the sterilisation chamber are of a disposable design.
According to a further aspect of the present invention there is provided a method of sterilisation comprising the steps of:
providing a sterilisation apparatus including an aerosol generator and a sterilisation chamber operatively coupled to each other;
locating an article requiring sterilisation in the sterilisation chamber; and
providing a recirculatory flow of an aerosol of a sterilising agent through the sterilisation chamber whereby in operation the recirculatory flow of the aerosol through the sterilisation chamber is effective in sterilising the article.
Preferably the method of sterilisation further comprises the step of condensing the aerosol within or on the article. More preferably the method additionally includes the step of rinsing and drying the aerosol having been condensed within or on the article.
Generally the sterilising agent includes hydrogen peroxide or a derivative thereof.
According to yet another aspect of the present invention there is provided a switching device being designed to activate upon detection of a low level of liquid within a reservoir, the switching device comprising a cavitation signal detector operatively coupled to an ultrasound generator which is electrically coupled to an ultrasonic transducer located adjacent or defining the reservoir, the cavitation signal detector being configured to deactivate the ultrasound generator upon detection up to a threshold level of cavitation wherein there is sufficient liquid within the reservoir.
Preferably the switching device also comprises a filter electrically coupled to and located xe2x80x9cupstreamxe2x80x9d of the cavitation signal detector, the filter being designed to filter all or part of the cavitation signal whereby said filtered portion only passes to the cavitation signal detector.
Typically the switching device also includes a blocking signal generator electrically coupled to a delay line which together operatively cooperate with the switching device to deactivate it when there is no cavitation.
Sterilisation is to be understood as including higher level disinfection.